Explanatory style, the habitual ways in which individuals explain bad events, was extracted from open-ended questionnaires filled out by 99 graduates of the Harvard University classes of 1942-1944 at age 25. Physical health from ages 30 to 60 as measured by physician examination was related to earlier explanatory style. Pessimistic explanatory style (the belief that bad events are caused by stable, global, and internal factors) predicted poor health at ages 45 through 60, even when physical and mental health at age 25 were controlled. Pessimism in early adulthood appears to be a risk factor for poor health in middle and late adulthood.